[Tilesathome] less inkscape runs

[Dirk-Lüder Kreie]

Dirk-Lüder Kreie schrieb:
> spaetz schrieb:
>> On Thu, Aug 21, 2008 at 11:17:05AM +0200, Dirk-L?der Kreie wrote:
>>
>>> You are aware that the stripes are not equal in height, which is 
>>> precisely why there are 32 calls at z 17 (instead of 1024 as it used 
>>> to be, BTW)
>>
>> They aren't? Isn't it always 256px height stripes? I see there is a 
>> reason why I haven't dared touching the main rendering functions yet. :-)
> 
> If you remember the white borders Batik error, that one resulted because 
> the svg is not exported 1:1 but slightly squished (one way or the 
> other). this squishing is dependent on latitude, so the stripe height in 
> the PNG will always be the same (256px), but not in the svg source.
> 
> This works around the osmarender projection bug.
> 
> I made some tests with a perl program that gave me the arithmetic and 
> projected middle-line of several tiles, and I found the maxError to be 
> around 0.6px for z12/13, and 0.03px for z16/17 (PNG tile pixels, that 
> is), so we could use the splitImage function from tilesPipeAtHome to 
> enhance our existing splitImageX to handle the entire svg area at once, 
> and just live with a bit more than half a pixel inaccuracy at z12/13.
> 
> However this will *not* work for caption rendering, as the error at z6 
> is tens of pixels.

I forgot: IIRC there has been some osmarender work to use correct 
projection, especially for the label placement in z6, these are related, 
and if the projection issue was fixed, then we can cut after export, 
without problem, at any zoom.

I forget which one was fixed, though, or/p or XSLT.

-- 

Dirk-Lüder "Deelkar" Kreie
Bremen - 53.0952°N 8.8652°E

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